Besides broad coverage and large program capacity, the most excellent characteristic of digital broadcast is its broadcast capability which can be point-to-points and point-to-face, and the cost of broadcasting information is not related to quantity of users. Thus, as an important component of information communication industry, the digital broadcast plays an important role in the construction of national information infrastructure and realization of normal service and national information security strategy.
In digital broadcasting service, the entire country is normally divided into districts, which also can be divided into multi-levels, each district can be configured with a plurality of broadcasting signal transmitters. To facilitate the receiving end obtaining the source of the received signal, the transmitter has to be identified in the transmitting signals. And these identified signals are generally represented in form of pseudo-random sequences. Further, to facilitate detecting the identifier signals of the transmitter by the receiver, it is preferable that these identifier signals have orthogonal properties.
In an OFDM system, a sampling rate is normally higher than a bandwidth of the system, for example, a bandwidth of 8 MHz with a sampling rate of 10 MHz. However, generally, a random sequence generating device generates a random sequence on the time-domain directly. For example, after a m-sequence generator generates a m-sequence x(n), a time-domain random sequence is generated by BPSK mapping. When the sampling rate is 10 MHz, the bandwidth of the sequence is at least 10 MHz, which may exceed the limit of the system bandwidth.